In recent years, an interface circuit for differential signal processing has been widely adopted in various devices as a standard interface for data transmission because of its resistance to noise and high speed data transmission.
Below, the difference between a differential signal method and a single ended signal method is explained with reference to FIGS. 7 and 8.
FIG. 7(a) is a diagram illustrating a schematic configuration of an interface circuit for differential signal processing. FIG. 7(b) is a diagram illustrating a schematic configuration of an interface circuit for single ended signal processing.
As shown in FIG. 7(a), the differential signal method transfers a signal employing two signal lines and the potential difference between the above two signal lines that transmit the differential signals determines whether the signal is “H” or “L”.
On the other hand, as illustrated in FIG. 7(b), the single ended signal method transfers a signal employing one signal line, and the potential difference from the ground (GND) determines whether the signal is “H” or “L”.
FIG. 8(a) is a diagram illustrating an example of a differential signal pair that is generated on the transmission side of the interface circuit for differential signal processing shown in FIG. 7(a) and supplied to the two signal lines.
FIG. 8(b) is a diagram illustrating a signal that is generated on the reception side of the interface circuit for differential signal processing shown in FIG. 7(a) and is outputted.
As illustrated in FIG. 8(a), since the differential signal pair, which is supplied by the two signal lines, uses the potential difference between a pair of differential signals, a small amplitude is maintained, allowing high speed transmission.
Further, as illustrated in the diagram, because the potential difference between the differential signal pair is used, even if noise is generated in the two signal lines, the noise is canceled out, providing a method resistant to noise.
On the other hand, FIG. 8(c) is a diagram illustrating an example of a single ended signal.
As illustrated in the diagram, because the single ended signal uses the potential difference from the ground (GND), in order to output a signal with the same potential level as the differential signal method, the amplitude of the signal becomes relatively large, hindering high speed data transmission.
Moreover, in case of the single ended signal, unlike the differential signal method, noise generated in the signal line is not cancelled out, thus providing a method susceptible to noise.
For the above reasons, the differential signal method has been widely adopted as a standard interface for data transmission.
An amplitude and a center potential of the differential signal used in the above differential signal method can be set appropriately for each individual device and a terminating resistance value provided on the reception side of the interface circuit for differential signal processing can be set appropriately for each individual device.
Further, Patent Document 1 discloses an interface circuit that supports both the single ended and the differential signal communication methods as well as a pair of input terminals for the differential signal that also serves as an input/output terminal of the single ended signal.
Moreover, in the configuration of the above Patent Document 1, the differential signal reception circuit receiving the differential signals is activated by inputting the differential signal to a separate exclusive input terminal of the differential signal from a combination terminal that serves as the input terminal of the differential signal and the input/output terminal of the single ended signal, and the activation state after activation is maintained by a built-in controller.
Patent Document 1 describes that such a configuration can suppress the possibility of the differential signal reception circuit being terminated at an unintended timing.